The present invention relates to a cam drive for a valve control in a valve-controlled internal combustion engine, especially in a mixture-lubricated internal combustion engine.
A mixture-lubricated, valve-controlled internal combustion engine is disclosed in DE 198 48 890 A1. The mixture is supplied to the internal combustion engine in the cylinder via an intake passage that is controlled by an intake valve. To lubricate the moving parts of the engine, the valve chamber communicates with the intake passage via a connection opening, whereby the crankcase is connected to the valve chamber via a further flow connection. This flow connection can be provided by the cam drive, since the latter is driven by the crankshaft and the poppet valves that are disposed in the cylinder heads must be actuated. In this connection, the pressure pulses in the intake passage are adequate to supply mixture to the chambers that are connected only via the connection opening.
For the correct control of the poppet valves in terms of time, control cams having cam noses are provided and are rotatably driven by the crankshaft. Due to the high speeds of such small-volume internal combustion engines, a lack of lubricant can occur, especially in the region of the control cams. Due to the great circumferential speeds of the control cams, a tractive flow that rotates about the axis of rotation of the cams can form in the cam chamber, so that the lubricating oil particles that are carried along in the mixture are displaced outwardly away from the lubricating locations. The lack of lubricating oil caused thereby leads to premature wear.
It is therefore an object of the present invention to improve the known cam drive in such a way that even at high and maximum speeds of the internal combustion engine, a reliable lubrication of the cam drive is ensured.